Several thousand infants are born in America each year with congenital cataracts which prevent normal visual input from reaching the retina of the affected eye. The objective of our research is to study the effect of such deprivation on visual development. Specifically, we will measure seven aspects of the vision of children treated for congental cataract: The development of visual acuity, contrast sensitivity, the symmetry of optokinetic nystagmus, color vision, color fields, the discrimination of form, and binocularity. Research in animals suggests that some of these aspects are affected more seriously by deprivation than are others. We will attempt to determine whether the timing and duration of deprivation influence the outcome on each of these measures by comparing results from children treated for congenital cataract at various ages to those from children treated for traumatic or developmental cataract. In cases of unilateral congenital cataract, we will also measure the extent to which patching the normal eye influences the development of vision in the aphakic eye. These data will indicate whether the deprivation caused by a cataract affects similarly the development of vision in humans and animals. They will also indicate whether congenital cataracts can be treated most effectively by early surgery, by fitting the aphakic eye with contact lenses to correct the refractive error, and, in unilateral cases, by aggressive patching of the normal eye. Since addressing these issues involves measuring the development of visual resolution, a final objective is to assess the validity of preferential looking and of optokinetic nystagmus as measures of visual resolution in infants and toddlers. This information will aid not only in interpreting our data from children treated for congenital cataract, but also will indicate whether the measures provide a valid basis for evaluating the prognosis of babies with other ocular abnormalities.